Guiding introducer system for use in the right atrium

ABSTRACT

A guiding introducer system for use in the right atrium comprised of an inner guiding introducer and an outer guiding introducer wherein the inner guiding introducer is comprised of a first and second section and the outer guiding introducer is comprised of a first, second and third section. The guiding introducer system is for use in sensing, pacing, and ablating procedures within the right atrium of the human heart.

This application is a division of application Ser. No. 08/333,759, filedNov. 3, 1994, now U.S. Pat. No. 5,628,316, which application is acontinuation-in-part of application Ser. No. 08/146,744, filed Nov. 3,1993, now U.S. Pat. No. 5,427,119.

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention relates to introducers. More particularly, this inventionrelates to a guiding introducer system for use within the right atriumof the human heart.

2. Prior Art

Introducers and catheters have been in use for medical procedures formany years. For example, one use has been to convey an electricalstimulus to a selected location within the human body. Another use isthe monitoring of measurements for diagnostic tests within the humanbody. Thus, catheters may be used by a physician to examine, diagnoseand treat while positioned at a specific location within the body whichare otherwise inaccessible without more invasive procedures. Cathetersmay be inserted into a major vein or artery which is near the bodysurface. The catheters are then guided to the specific location forexamination, diagnosis or treatment by manipulating the catheter throughthe artery or vein of the human body.

Catheters have become increasingly useful in remote and difficult toreach locations within the body. However, the utilization of thesecatheters is frequently limited because of the need for the preciseplacement of the tip of the catheter at a specific location within thebody.

Control of the movement of catheters to achieve such precise placementis difficult because of the inherent structure of a catheter. The bodyof a conventional catheter is long and tubular. To provide sufficientcontrol of the movement of the catheter, it is necessary that itsstructure be somewhat rigid. However, the catheter must not be so rigidas to prevent the bending or curving necessary for movement through thevein, artery or other body part to arrive at the specified location.Further, the catheter must not be so rigid as to cause damage to theartery, vein or body part while it is being moved within the body.

While it is important that the catheter not be so rigid as to causeinjury, it is also important that there be sufficient rigidity in thecatheter to accommodate torque control, i.e., the ability to transmit atwisting force along the length of the catheter. Sufficient torquecontrol enables controlled maneuverability of the catheter by theapplication of a twisting force at the proximal end of the catheter thatis transmitted along the catheter to its distal end. The need forgreater torque control often conflicts with the need for reducedrigidity to prevent injury to the body vessel.

Catheters are used increasingly for medical procedures involving thehuman heart. In these procedures a catheter is typically advanced to theheart through veins or arteries and then is positioned at a specifiedlocation within the heart. Typically, the catheter is inserted in anartery or vein in the leg, neck, upper chest or arm of the patient andthreaded, often with the aid of a guidewire or introducer, throughvarious arteries or veins until the tip of the catheter reaches thedesired location in the heart.

The distal end of a catheter used in such a procedure is sometimespreformed into a desired curvature so that by torquing the catheterabout its longitudinal axis, the catheter can be manipulated to adesired location within the heart or in the arteries or veins associatedwith the heart. For example, U.S. Pat. No. 4,882,777 discloses acatheter with a complex curvature at its distal end for use in aspecific procedure in the right ventricle of a human heart. U.S. Pat.No. 5,231,994 discloses a guide catheter for guiding a balloon catheterfor the dilation of coronary arteries. U.S. Pat. No. 4,117,836 disclosesa catheter for the selective coronary angiography of the left coronaryartery and U.S. Pat. Nos. 5,299,574, 5,215,540, 5,016,640 and 4,883,058disclose catheters for use in selective coronary angiography of theright coronary artery. See also U.S. Pat. No. 4,033,5741. Finally, U.S.Pat. No. 4,898,591 discusses a catheter with inner and outer layerscontaining braided portions. The '591 patent also discloses a number ofdifferent curvatures for intravascular catheters.

In addition to single catheters with various curvatures, U.S. Pat. No.4,581,017 discloses an inner and outer guide catheter, numbers 138 and132, for use with a balloon catheter for treatment of coronary arteries.U.S. Pat. No. 5,267,982 discloses a catheter assembly and methods forcatheterization of coronary arteries wherein an inner catheter (50) andouter catheter (52) are used in combination for the treatment of rightand left coronary angiographic procedures. See also U.S. Pat. No.4,935,017 which discloses a similar device. U.S. Pat. No. 5,290,229discloses a straight outer sheath and a preformed inner catheter for usein the heart. See also U.S. Pat. Nos. 5,304,131, 5,120,323, 4,810,244and 5,279,546.

Thus, there are a number of patents which disclose catheters withpredetermined shapes, designed for use in specific medical proceduresgenerally associated with the heart or the vascular system. Because ofthe precise physiology of the heart and the vascular system, cathetersor introducers with carefully designed shapes for predetermined useswithin the human heart and vascular system are important.

The sources of energy used for catheter ablation vary. Initially, highvoltage, direct current (DC) ablation techniques were commonly used.However, because of problems associated with the use of DC current,radio frequency (R.F.) ablation has become a preferred source of energyfor the ablation procedures. The use of RF energy for ablation has beendisclosed, for example, in U.S. Pat. Nos. 4,945,912, 5,209,229,5,281,218, 5,242,441, 5,246,438, 5,281,213 and 5,293,868. Other energysources being considered for ablation of heart tissue include laser,ultrasound, microwave and direct current fulgutronization procedures.Also disclosed have been procedures where the temperature about thecatherization probe is modified.

Catheter ablation of accessory pathways associated withWolfe-Parkinson-White syndrome using a long vascular sheath by both atransseptal and retrograde approach is discussed in Saul, J. P., et al."Catheter Ablation of accessory Atrioventricular Pathways in YoungPatients: Use of long vascular sheaths, the transseptal approach and aretrograde left posterior parallel approach" Journal of the AmericanCollege of Cardiology, Vol. 21, no. 3, pps. 571-583 (Mar. 1, 1993). Seealso Swartz, J. F. "Radiofrequency Endocardial Catheter Ablation ofAccessory Atrioventricular Pathway Atrial Insertion Sites" Circulation,Vol. 87, no. 2, pps. 487-499 (February, 1993).

Accordingly, it is an object of this invention to prepare a dual guidingintroducer system for selected medical procedures in the right atrium.

It is a further object of this invention to prepare a dual guidingintroducer system for use in selected electrophysiology procedureswithin the right atrium of the heart.

Another object of this invention is to prepare a dual guiding introducersystem for use in selected ablation procedures within the right atriumof the heart.

These and other objects are obtained by the design of the guidingintroducer system disclosed in the instant invention.

SUMMARY OF INVENTION

The instant invention is a guiding introducer system for selectedmedical procedures in the right atrium. It is comprised of an innerguiding introducer and an outer guiding introducer. A dilator ispreferably used with the guiding introducer system, which dilator may bea standard dilator used with conventional introducers. The inner guidingintroducer is a shaped introducer comprised of a first and secondsection, wherein the first section is a generally elongated straightsection which is merged at its distal end with the second section whichis a simple curved section. The outer guiding introducer is comprised ofa first, second and third sections, wherein the first section is agenerally elongated straight section which is merged at its distal endwith the second and third sections which form complex curved sections.The inner guiding introducer is longer than the outer guiding introducerto permit it to extend out from the lumen of the outer guidingintroducer to form various curves and shapes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of the right side of the heart showing theright atrium and the placement of the guiding introducer system.

FIG. 2 is a perspective view of the dilator.

FIG. 3 is a perspective view of the inner guiding introduce.

FIG. 4 is a perspective view of the outer guiding introducer.

FIG. 5 is a perspective view of the inner and outer guiding introducersin combination with the distal end of the inner guiding introducerextended from the distal end of the outer guiding introducer.

DETAILED DESCRIPTION OF THE DRAWINGS

A typical human heart includes a right ventricle, a right atrium, leftventricle and left atrium. The right atrium is in fluid communicationwith the superior vena cava and the inferior vena cava. Theatrioventricular septum separates the right atrium from the rightventricle. The tricuspid valve contained within the atrioventricularseptum communicates the right atrium with the right ventricle. On theinner wall of the right atrium where it is connected with the leftatrium is a recessed portion, the fossa ovalis. See FIG. 1. In the heartof a fetus, the fossa ovalis is open, permitting the fetal blood to flowbetween the right and left atria. In most individuals, this openingcloses after birth, but in as many as 25 percent of individuals anopening still remains in the fossa ovalis between the right and leftatria. Between the fossa ovalis and the tricuspid valve is the openingor ostium for the coronary sinus. The coronary sinus is the largeepicardial vein which accommodates most of the venous blood which drainsfrom the myocardium into the right atrium.

In the normal heart, contraction and relaxation of the heart muscle(myocardium) takes place in an organized fashion as electro-chemicalsignals pass sequentially through the myocardium from the atrial to theventricular tissue along a well defined route which includes theHis-Purkinje system. Initial electrical impulses are generated at thesinuatrial (SA) node and conducted to the atrioventricular (AV) node.The AV node lies near the ostium of the coronary sinus in theinteratrial septum in the right atrium. The His-Purkinje system beginsat the AV node and follows along the membranous interatrial septumtoward the tricuspid valve through the atrioventricular septum and intothe membranous interventricular septum. At about the middle of theinterventricular septum, the His-Purkinje system splits into right andleft branches which straddle the summit of the muscular part of theinterventricular septum.

Sometimes abnormal rhythms occur in the heart which are referred to asarrhythmia. For example, a common arrhythmia is Wolfe-Parkinson-Whitesyndrome (W-P-W). The cause of W-P-W is generally believed to be theexistence of an anomalous conduction pathway or pathways that connectsthe atrial muscle tissue directly to the ventricular muscle tissue, thusby-passing the normal His-Purkinje system. These pathways are usuallylocated in the fibrous tissue that connects the atrium and theventricle. In recent years a technique has been developed to destroythese anomalous conduction pathways by delivering energy into the tissuein which the pathways exist. To accomplish this procedure a specialelectrode catheter is positioned as close as possible to the anomalousconduction pathway to maintain constant tissue contact while energy isdelivered to the cardiac tissue to destroy the pathway. This same typeof contact with the cardiac tissue is also necessary when mapping orother such procedures are employed relating to these pathways.

One end of these anomalous conduction pathways can be located either inthe right atrium or in the left atrium with the other end of the pathwaylocated in the corresponding ventricle. When the anomalous conductionpathway is located between the left atrium and the left ventricle, thereare two approaches to positioning the catheter near the pathway for theappropriate medical procedure. One is to introduce the catheter into thefemoral artery by a standard introducer sheath and advance it up theaorta, across the aortic valve into the left ventricle and then attemptto position its tip under the mitral valve annulus near the anomalousconduction pathway. This approach is frequently difficult for manyreasons, including the structure of the left ventricle, the fact that itrequires arterial access and potential problems associated with ablationof ventricular tissue including the possibility of creation of asubstrate for a future arrhythmia which could result in sudden cardiacdeath. The other approach is to introduce a transseptal sheathapparatus, a long single plane curve introducer, into the right femoralvein and advance it through the inferior vena cava into the rightatrium. A puncture is then made through the fossa ovalis in theinteratrial septum and the apparatus is advanced into the left atriumwhere the trocar and dilator of the apparatus are removed, leaving theintroducer in position in the left atrium. The mapping or ablationcatheter is then inserted through the introducer and into the leftatrium and positioned on top of the mitral valve annulus near theanomalous conduction pathway. Specific positions may be chosen for themapping or ablation on the left side of the heart, includingspecifically posteroseptal, posterior, posterolateral, lateral andanterolateral positions around the mitral valve annulus.

Traditionally, there have been two techniques for locating and ablatinganomalous conduction pathways which are situated between the rightatrium and right ventricle. Either method can be initiated by advancinga catheter through an access site into a vein in the leg, neck or upperchest.

The first technique, which approaches the pathway from the pathway'sventricular insertion site, involves entering the right atrium fromeither the inferior or superior vena cava, passing through the tricuspidvalve, and advancing toward the apex of the right ventricle. Then thecatheter is directed to make a 180 degree turn to reverse its path backup toward the right atrium and locate the accessory pathway under thetricuspid valve apparatus. The accessory pathway is then ablated fromthe ventricular insertion site under the tricuspid valve.

The second technique, which approaches the pathway from the atrialinsertion site, is to enter the right atrium from the inferior orsuperior vena cava, and attempt to locate the atrial insertion site ofthe accessory pathway around the tricuspid valve annulus. The accessorypathway is then ablated from the pathway's atrial insertion site on theatrial aspect of the tricuspid valve.

AV nodal pathways can be located and ablated from the right atrium.

Mere introduction of the catheter into the right atrium is notsufficient to effectively and efficiently perform these medicalprocedures, especially the mapping or ablation of the anomalousconduction pathways. These medical procedures are usually performedusing a specific catheter. The medical practitioners monitor theintroduction of the catheter and its progress through the vascularsystem by a fluoroscope. However, such fluoroscopes do not easilyidentify the specific features of the heart in general and thecritically important structures of the right atrium in specific, thusmaking placement of the catheter difficult. This placement is especiallydifficult as the beating heart is in motion and the catheter will bemoving within the right atrium as blood is being pumped through theheart throughout the procedure. The structure and shape of the guidingintroducer of the instant invention addresses and solves these problems.

The dual guiding introducer system for use in the right atrium iscomprised of an inner and an outer guiding introducer. See FIG. 5. Adilator is also preferably used wherein the dilator is preferably aconventional dilator used with cardiac procedures and is not generallycurved. See FIG. 2. The standard length of the dilator is about 60 toabout 80 cm.

The inner guiding introducer is generally comprised of two sections. SeeFIG. 3. The first section is a conventional generally elongated hollowstraight catheter section of sufficient length for introduction into thepatient and for manipulation from the point of insertion to the specificdesired location within the heart. Merged with the distal end of thefirst section of the guiding introducer, but an integral part of theentire guiding introducer, is the second section which is a curvedsection, curved in a simple curve with a radius of about 0.5 to about2.0 in., preferably about 0.7 to about 1.3 in. to form an arc ofapproximately 150 to about 270 degrees, preferably about 170 to about190 degrees ending in a distal tip.

The outer guiding introducer for use in the right atrium is comprised ofa first, second and third section. See FIG. 4. (As with the innerguiding introducer, this division into three separate sections is forease of illustration. The guiding introducer is preferably formed in asingle procedure with each section an integral part of the overallguiding introducer.) The first section is a conventional, generallyelongated hollow straight catheter section of sufficient length forintroduction into the patient and for manipulation from the point ofinsertion to the specific desired location within the heart. Merged withthe distal end of the first section of the guiding introducer is thesecond section which is comprised of a curved section and a straightsection, wherein the curved section curves upward as shown in FIG. 4 ina longitudinal curve with a radius from about 0.25 to about 0.75 cm.,preferably about 0.4 to about 0.6 in. to form an arc of approximately 40to about 60 degrees, preferably about 45 to about 55 degrees. Mergedwith the distal end of this curve is the straight section from about 0.4to about 0.7 in. in length, preferably about 0.55 to about 0.65 in. inlength. At the distal end of the second section is the third section.The third section is comprised of a curved section with a radius ofabout 0.5 to about 1.5 in. and preferably about 0.8 to about 1.2 in.with an arc of about 30 to about 60 degrees, and preferably about 35 toabout 55 degrees, which ends in the distal tip of the outer guidingintroducer. The curved section of the third section curves inapproximately the same plane as the curve of the second section (withinabout 15 degrees of coplanar).

By extending the distal tip of the inner guiding introducer away fromthe distal tip of the outer guiding introducer and by rotating the innerguiding introducer with respect to the outer guiding introducer, avariety of shapes of the overall guiding introducer system are formed todirect a mapping and/or ablation catheter toward the site within theatrium of interest. See FIG. 5. These shapes permit ablation procedureswithin the right atrium to be performed, for example, postero septal andseptal accessory pathways. By further extension of the inner guidingintroducer, accessory pathways located anterioseptal to anterior can betreated. Further extension of the inner guiding introducer within theouter guiding introducer permits analysis of treatment of anterior toanteriolateral accessory pathways. By further extension, treatment isavailable for accessory pathways located anterolateral to lateral to thetricuspid valve annulus. In addition, by manipulation of the innerguiding introducer within the outer guiding introducer, additionalprocedures can be performed within the right atrium, for example, fortreatment of ectopic atrial tachycardia or even for certain atrialfibrillation procedures. Being able to extend the inner guidingintroducer within the outer guiding introducer and to rotate the innerguiding introducer within the outer guiding introducer permits a widevariety of overall shapes which is particularly useful to medicalpractitioners. The medical practitioner is able to determine therelative location of the inner and outer guiding introducers because oftip markers located near the distal tip of both the inner and outerguiding introducers.

The distal tip of both the inner and outer guiding introducers may be,and generally will be, tapered to form a good transition with thedilator.

The relative size of the outer guiding introducer in relation to theinner guiding introducer should be sufficient to permit the innerguiding introducer to be torqued or rotated within the outer guidingintroducer without undue restriction on such movement. Preferably, thedifference in size between the inner and outer guiding introducer shouldbe at least about 3 "French" (1 French equals about one-third of amillimeter). For example in one preferred embodiment, the outer guidingintroducer is 11 French in size and the inner guiding introducer is 8French. By this difference in diameter, there is approximately 1 Frenchunit of volume between the outer surface of the inner guiding introducerand the inner surface of the outer guiding introducer. Preferably, thisvolume of space between the inner and outer guiding introducer is filledwith a biocompatible solution, such as a saline solution, preferably aheparinized saline solution. This saline solution also provideslubricity to the two introducers, allowing more accurate torquing of theenhanced inner guiding introducer within the outer guiding introducer.In addition, it is preferable that the structure of both the inner andthe outer guiding introducer have a high torsional constant to allow forthe full utilization of the various shapes available by rotation andextension of the inner and outer guiding introducer. To permit this hightorsional constant, in one preferred embodiment the inner guidingintroducer is braided to provide further strength and structuralstability.

The guiding introducer may be made of any material suitable for use inhumans, which has a memory or permits distortion from and subsequentsubstantial return to the desired three dimensional or complexmulti-planar shape. For the purpose of illustration and not limitation,the internal diameter of the tip of the guiding introducers may varyfrom about 6 to about 10 "French" Such introducers can accept dilatorsfrom about 6 to about 10 French and appropriate guidewires. Obviously iflarger, or smaller dilators and catheters are used in conjunction withthe guiding introducers of the instant invention, modification can bemade in the size of the instant guiding introducers.

The pair of guiding introducers preferably contain one or a multitude ofradiopaque tip marker bands near the distal tip of the guidingintroducers. Various modifications may be made in the shapes byincreasing or decreasing its size or adding additional tip markers.

The inner and outer guiding introducers also preferably contain one or aplurality of vents near the distal tip of the guiding introducers,preferably 3 or 4 or such vents. The vents are preferably located nomore than about 5 to 6 cm. from the tip of the guiding introducers andmore preferably 0.5 cm. to about 4.0 cm. from the tip. The size of thesevents should be in the range of about 20 to 60 1/1000 of an inch indiameter. These vents are generally designed to prevent air embolismsfrom entering the guiding introducers caused by the withdrawal of acatheter contained within the guiding introducers in the event thedistal tip of the guiding introducers is occluded. For example, if thetip of the inner guiding introducer is placed against the myocardium andthe catheter located within the inner guiding introducer is withdrawn, avacuum may be created within the inner guiding introducers if no ventsare provided. If such vacuum is formed, air may be forced back into theguiding introducer by the reintroduction of a catheter into the lumen ofthe guiding introducers. Such air embolism could cause problems for thepatient including the possibility of a stroke, heart attack or othersuch problems common with air embolism in the heart. The addition ofvents near the distal tip of the guiding introducers prevents theformation of such vacuum by permitting fluid, presumably blood, to bedrawn into the lumen of the guiding introducers as the catheter is beingremoved, thus preventing the possibility of formation of an airembolism.

Variances in size or shape of the pair of guiding introducer are alsointended to encompass pediatric uses for the pair of guiding introducersof the instant invention, although the preferred use is for adult humanhearts. It is well recognized that pediatric uses may require reductionsin size of the various sections of the guiding introducers in particularthe first section, but without any significant modification to the shapeor curves of the guiding introducers. However, because incrementalchanges can be made in the overall shape of the pair of guidingintroducers, the system can better adjust to differing shapes and sizesof heart than can a single guiding introducer.

In operation, a modified Seldinger technique is normally used for theinsertion of a catheter into either an artery or vein of the body. Usingthis procedure, a small skin incision is made at the appropriatelocation to facilitate the catheter and dilator passage. Thesubcutaneous tissue is then dissected, followed by a puncture of thevessel with an appropriate needle with stylet positioned at a relativelyshallow angle. The needle is then partially withdrawn and reinserted ata slightly different angle into the vessel, making sure that the needleremains within the vessel. A soft flexible tip of an appropriate sizedguidewire is then inserted through and a short distance beyond theneedle into the vessel. Firmly holding the guidewire in place, theneedle is removed. The guidewire is then advanced through the vesselinto the inferior vena cava or the right atrium. With the guidewire inplace, either in the inferior vena cava or into the right atrium, thedilator is then placed over the wire with the pair of guidingintroducers placed over the dilator. The dilator and pair of guidingintroducers generally form an assembly to be advanced together along theguidewire into the inferior vena cava or into the right atrium. Theguidewire is then withdrawn as is the dilator, leaving the pair ofguiding introducers either in the inferior vena cava or in the rightatrium. If the pair of guiding introducers has been left in the inferiorvena cava, it is then advanced up the inferior vena cava into the rightatrium. By extending and withdrawing the inner guiding introducer fromthe outer guiding introducer and by rotating the inner guidingintroducer within the outer guiding introducer, great variances in theoverall shape of the guiding introducer system can be achieved.

By movement of the inner guiding introducer within the outer guidingintroducer in conjunction with fluoroscopic viewing, the distal portionof the outer guiding introducer can be manipulated to direct the distalend of a catheter placed within the lumen of the inner guidingintroducer to a specific internal surface within the right atrium. SeeFIG. 5. In addition, by providing sufficient rigidity, the distal end ofthe inner guiding catheter can be maintained in that fixed location orsurface position of the endocardial structure to permit the appropriateprocedures to be performed. If sensing procedures are involved, the pairof guiding introducers is placed in the desired location. At that point,the electrical activity of the heart peculiar to that location can beprecisely determined by use of an electrophysiology catheter placedwithin the guiding introducer. Further, as the pair of guidingintroducers permit precise location of catheters, an ablation cathetermay be placed at a precise location for destruction of the cardiactissue by the use of energy, for example, radio frequency, thermal,laser or direct current (high energy direct, low energy direct andfulgutronization procedures). The precise placement of the ablationcatheter tip on the cardiac tissue is important as there will be nodilution of the energy delivered due to unfocused energy beingdissipated over the entire cardiac chamber and lost in the circulatingblood by a constant movement of the tip of the ablating catheter. Thispermits a significantly reduced amount of energy to be applied, whilestill achieving efficient ablation. Further, time used to perform theprocedure is significantly reduced over procedures where no guidingintroducers are used.

It will be apparent from the foregoing that while particular forms ofthe invention have been illustrated and described, various modificationscan be made without departing from the spirit and scope of theinvention. Accordingly, it is not intended that this invention belimited except as by the appended claims.

We claim:
 1. A guiding introducer system to be used in the right atriumof a human heart comprising a precurved cardiac chamber inner guidingintroducer and a precurved cardiac chamber outer guiding introducerwherein said guiding introducers are used in combination in a chamber ofthe heart whereby the guiding introducers are structurally stabalized toenhance their rigidity to assist in the control of their movement withinthe chamber of the heart.
 2. The guiding introducer system of claim 1further comprising a dilator, wherein said dilator is generallystraight.
 3. The guiding introducer system of claim 1 wherein the innerguiding introducer comprises a first and second section each withproximal and distal ends, wherein the first section is a generallyelongated straight section, wherein merged with the distal end of saidfirst section is the second section which is a curved section with aradius of about 0.5 to about 1.5 in. to form an arc of approximately 150to 270 degrees ending in the distal end of the second section of theinner guiding introducer.
 4. The guiding introducer system of claim 1wherein the outer guiding introducer comprises, a first, second andthird section, each with distal and proximal ends, wherein the firstsection is a generally elongated straight section, wherein merged withthe distal end of said first section is the second section whichcomprises a curved portion and a straight portion, wherein the curvedportion has a radius of about 0.25 in. to about 0.75 in. to form an arcof about 40 to 60 degrees, wherein the straight portion of the secondsection is from about 0.4 to about 0.7 in. in length, wherein mergedwith the distal end of the second section is the third section, whereinsaid third section comprises a curved portion with a radius of about 0.5to about 1.5 in. to form an arc of about 30 to about 60 degrees andwherein the third section is generally coplanar with the second sectionending in the distal end of the third section of the outer guidingintroducer.
 5. The guiding introducer system of claim 3 wherein aplurality of vents is provided near the distal end of the second sectionof the inner guiding introducer.
 6. The guiding introducer system ofclaim 4 wherein a plurality of vents is provided near the distal end ofthe third section of the outer guiding introducer.
 7. The guidingintroducer system of claim 3 wherein tip markers are contained withinthe inner guiding introducer.
 8. The guiding introducer system of claim4 wherein tip markers are contained within the outer guiding introducer.